This is a font containing the Ath characters used to write the Baronh language, which was created by Morioka Hiroyuki and used in Sekai no Monshou. More information can be found here: [link]

Edit: I've uploaded a new version, which now has all the numbers and some improvements to the letters. This update has been expedited especially for "Llumina", a French fansubbing group which is planning to use the font for "Sekai no Senki 3".